text: Limit color matrices cache size

text/text.go

@@ -124,8 +124,13 @@ func fixed26_6ToFloat64(x fixed.Int26_6) float64 {
 	return float64(x) / (1 << 6)
 }
 
+type colorMCacheEntry struct {
+	m     ebiten.ColorM
+	atime int64
+}
+
 var (
-	colorMCache = map[color.Color]ebiten.ColorM{}
+	colorMCache = map[color.Color]*colorMCacheEntry{}
 )
 
 func (g *glyph) draw(dst *ebiten.Image, x, y fixed.Int26_6, clr color.Color) {
@@ -138,17 +143,34 @@ func (g *glyph) draw(dst *ebiten.Image, x, y fixed.Int26_6, clr color.Color) {
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Translate(fixed26_6ToFloat64(x+b.Min.X), fixed26_6ToFloat64(y+b.Min.Y))
 
-	cm, ok := colorMCache[clr]
-	if !ok {
+	e, ok := colorMCache[clr]
+	if ok {
+		e.atime = now()
+	} else {
+		if len(colorMCache) >= 256 {
+			var oldest color.Color
+			t := int64(math.MaxInt64)
+			for key, e := range colorMCache {
+				if e.atime < t {
+					t = g.atime
+					oldest = key
+				}
+			}
+			delete(colorMCache, oldest)
+		}
+		cm := ebiten.ColorM{}
 		rf := float64(cr) / float64(ca)
 		gf := float64(cg) / float64(ca)
 		bf := float64(cb) / float64(ca)
 		af := float64(ca) / 0xffff
-		cm.Reset()
 		cm.Scale(rf, gf, bf, af)
-		colorMCache[clr] = cm
+		e = &colorMCacheEntry{
+			m:     cm,
+			atime: now(),
+		}
+		colorMCache[clr] = e
 	}
-	op.ColorM = cm
+	op.ColorM = e.m
 
 	a := atlases[g.char.face][g.char.atlasGroup()]
 	sx, sy := a.at(g)